Mat switches



July 15 1958 F. J. osucH ETAL 2,843,695

- MAT SWITCHES Filed Dec. 1o, 195e lvm EI El A@ (al I 425.! I

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MAT SWITCHES Application December 10, 1956, Serial No. 627,194

1 Claim. (Cl. 20G- 86) This invention relates generally to electrical switches and particularly to weight operated mat type switches.

As is well known, mat type switches are suitable, among other uses, for controlling the opening and closing of barriers, such as the doors of stores and the doors and gates of industrial plants. These mat type switches are operated by the weight of a person stepping onto them or by a vehicle depressing the mat and as a consequence are subject to hard usage and early failure. The requirements for a successful mat switch are that it be sensitive to the weight of `a child weighing say about fifty pounds, and yet be rugged tor, withstand repeated operation by heavy traffic, both pedestrian and vehicular over a long period of time. In addition, the mat switch must be so constructed as to insure against accumulation of moisture within the mat structure and resultant short circuiting of the switch. A

Accordingly one of the objects of the invention is to provide an improved mat type switch which meets the above mentioned requirements.

Another object of the invention is to provide a mat type switch which although sensitive in operation and durable for long usage is nevertheless inexpensive to produce.

Another object of the invention is to provide an improved mat type switch which has a resilient sheet constituting the movable contact that is of a character and arrangement with other components of the switch to provide sensitivity of operation without danger of the contact taking sets or otherwise damaged by heavy weights traversing the mat.

Other objects of the invention will become apparent from the following detail description, taken in connection with the accompanying drawing in which:

Fig. l is a plan view with parts broken away of a mat switch embodying features of the invention;

Fig. 2 is an enlarged fragmentary sectional view of the mat, taken along line 2-2 of Fig. l;

Fig. 3 is an enlarged fragmentary sectional view, taken along line 3--3 of Fig. l; and

Fig. 4 is an enlarged fragmentary sectional view, taken along line 4 4 of Fig. l.

Fig. 5 is a modification showing a sheet spacer having a plurality of adjacent holes.

Referring to the drawing by characters of reference, the mat has a base 20 which may be rectangular in shape, as shown, or any other desired shape. ln addition to being the base of the mat structure, the sheet 2i) also functions as one, or the xed contact of the switch and to this end is made of a suitable electric conducting material, such as sheet steel. The base sheet 20 is preferably solid in the sense that it is without holes and otherwise imperviousl to the passage of moisture therethrough.

Overlying the base sheet 20 is a second electric conducting sheet of metal 22 which constitutes the weight responsive contact of the switch. The sheet contact 22 is made of a thin, flexible and resilient material such arent C 2,843,695A Patented July 15, 1958 as spring steel which will deflect sufliciently to engage sheet contact 20 say under pressure of fifty pounds, and will return to its normal open circuit at condition upon removal of the pressure. The flexible sheet contact 22 is made solid, that is without any holes therethrough, so as to overcome one of the common causes of mat failure, namely permanent distortion of the flexible contact by the weight of heavy vehicles passing thereover. In addition, the solid sheets aid in preventing entrance of moisture into the space between the sheet contacts, thus overcoming another cause of mat failure which has been particularly prevalent in mats using a moisture retaining sponge rubber contact separator sheet.

To insure further against the possibility of heavy weights putting a permanent set in the sheet 22, we arrange the sheets 24), 22 in close proximity to each other so that only slight dellection of sheet 22 is required for it to engage sheet contact 20, To this end, the sheets 20 and 22 are separated from each other by a plurality of thin individual spacers 24. The spacers 24 may be made of any suitable electric insulating material, preferably a material which will notl appreciably compress or pack down over a long period of time. We have found it desirable to make the spacers 24 from any suitable nonconducting fabric, preferably adhesive tape. From such tape, the spacers 24 may be made about one quarter inch square and for best results, are arranged in rows about tive inches apart and the rows staggered, as shown. By this arrangement, the spacers 24 define areas of the upper sheet 22 that are free to flex downwardly under weight into contact with the lower sheet 20 to close the switch. Any other arrangement of the spacers 24 may be used so long as the arrangement is such as to prevent sagging of sheet 22 into contact with base contact 20.

It has been found that a very satisfactory mat switch is provided by making the lower contact Ztl of 18 gauge sheet steel, the upper contact 22 of 20 gauge resilient sheet steel, and the spacers 24 of .0l inch thickness, nonconducting adhesive tape. It will be understood that the above dimensions are variables and not limitations of the scope of the invention.

On the upper surface of the sheet 22 is a flexible rubber sheet 28 which serves to provide desired traction, insulation, and a finished appearance to the mat switch construction. Clamping strips 30 are preferably used to clamp the sheets 2t) and 22 and the rubber cover sheet 28 together around the peripheries thereof, and to give a finished appearance to the mat. Outer margins of the sheets 20 and 22 are preferably separated by strips 32 of adhesive tape, or other suitable spacer means of electric insulating material.

In the modication of Fig. 5, the sheet metal contacts may be the same as the contacts 20 and 22 of the above described mat switch. However, instead of separating the contacts by the plurality of individual spacers 24, the contacts are separated by a sheet spacer 34 in the form of a thin sheet of electric insulating material having a plurality of adjacent cutouts or holes that provide closely spaced open areas over the entire mat for engagement between overlying portions of the contact sheets when such portions are depressed. The spacer 34 may be made of any suitable electric insulating material, such as, a sheet of tough fabric like the material from which adhesive tape is made, or the spacer 34 may be made of a thin sheet of rubber or any suitable rubberized material. In any event, the thickness of the spacer 34 should preferably be about .0l of an inch so as to require only slight flexing of the upper sheet contact to' engage the lower contact and thus avoid early metal fatigue. The cutouts 36 in the spacer 34 should be about live or six inches in diameter and be arranged suiciently close together to approach as near as practical the proportional arrangement ofthe spacers 24 and open areas of the mat switch of Fig. l.

From the above description of the mat switch and modification thereof, it will be understood that the spacers 24 or 34 will keep the upper lexible sheet Y2,2 from sagging into engagement with the lower sheet 29, thus normally holding the switch in open circuit position. Since the sheet contacts and 22 are in close proximity and the area of each open space greatly exceeds the area of the surrounding spacer material, a person stepping onto the mat will deflect the trodden portions of upper sheet 22 into contact with the exposed portions of sheet 20, and keep the contacts closed. When the person steps off of the mat, the upper sheet contact 22 will spring back to its normal at state aided by the spacer material, returning the switch to its normally open position.

From the foregoing detail description, it will now be appreciated that we have provided a new and improved mat type switch of a structural character by which to effect both sensitivity of switch operation and long useful service. It will be understood that the provision of a mat switch contact in the form of a thin, solid7 and resilient sheet, spaced from its contact by spacer means of less thickness than the thickness of the resilient sheet insures a sensitive switch, yet one which will not be subject to deformation or be otherwise rendered inoperative by heavy vehicles passing over it. In addition, it will be noted that the interior of the mat switch structure is sealed against entrance of moisture, and that any moisture which might by accident find its way into the interior of the structure would not be absorbed and collected by any material therein which it might contact so that CIK i danger of short circuiting the switch by moisture is practically eliminated.

While We have shown and described our improved mat type switch in considerable detail, it is understood that the invention is to be limited only by the metes and bounds of the appended claim.

What I claim is:

A mat switch comprising, a moisture impervious sheet of metal constituting the base and one contact of the switch, a moisture impervious sheet of resilient metal of lesser thickness than the first and imposed above and in close proximity to the rst sheet, said second sheet constituting the other of the switch contacts, separate spacers of adhesive material interposed between said sheets and adhering to one of them, said spacers having a thickness less than the thickness of said resilient sheet and normally spacing said sheets apart, said spacers being spaced apart over the area of said one sheet in rows having the spacers of adjacent rows ollset and defining areas of flexibility of the resilient sheet, clamping means connecting said sheets together around the peripheral edges thereof and a rubber mat covering said resilient sheet and clamped by said clamping means to said rst sheet and insulating said sheets from each other around the peripheries thereof.

References Cited in the le of this patent UNITED STATES PATENTS 1,776,992 Broekman Sept 30, 1930 2,611,049 Roby sept. 16, 1952 2,773,148 Roby et al. Dec. 4, 1956 2,783,327 Luckey Feb. 26, 1957 

